The consanguinity of the Laccadive-Chagos mono-nematath, a thread ridge, with the tholeiitic magma plateau over the Indian sub-continent (Dietz and Holden, 1970), and the total intensity magnetic observations over the former, suggest that the Kori-Laccadive sector of the nematath represents a lateral spread of the Deccan Trap sequence. This is used here to estimate the time of geomagnetic field reversal, as observed from the palaeomagnetic investigations over the Deccan Traps, to be 3 m.y. younger than the Cretaceous-Cenozoic boundary. The tectonic implications have been discussed in the light of plate theory.